Electric surface type heating element and insulator combination

ABSTRACT

The present invention relates to a surface-type electric heating element including at least a pair of terminal pins extending from opposite ends of a convoluted sheath member, a blade carried by each terminal pin adapted for plug-in type connection, and an insulator permitting a lead-wire, screw-type connection of the surface unit to electric power. Because of the insulator both methods of connection of the surface-type electric heating element to electric power may be carried out with the terminal blades in the same disposition relative to the plane of the surface unit. The terminal blade includes a tapped thread to permit lead-wire, screw-type connection without the requirement of securing nuts.

United States Patent Skinner May 21, 1974 [75] Inventor: Charles A. Skinner, Laurel, Md.

[73] Assignee: Baxter Laboratories, Inc., Morton Grove, 111.

[22] Filed: Aug. 16, 1973 [21] Appl. No.: 389,045

[52] US. Cl 219/451, 219/467, 219/541,

339/217 [51] Int. Cl. H051) 3/68 [58] Field of Search 219/451, 452, 455, 458,

3,466,426 9/1969 Kefauver, Jr. 219/451 3,506,805 4/1970 Sauder 219/451 3,617,703 11/1971 Ewart, Jr. 219/451 Primary Examiner-Volodymyr Y. Mayewsky Attorney, Agent, or FirmRichard G. Kinney; Samuel B. Smith 5 7 ABSTRACT The present invention relates to a surface-type electric heating element including at least a pair of terminal pins extending from opposite ends of a convoluted sheath member, a blade carried by each terminal pin adapted for plug-in type connection, and an insulator permitting a lead-wire, screw-type connection of the surface unit to electric power. Because of the insulator both methods of connection of the surface-type electric heating element to electric power may be carried out with the terminal blades in the same disposition relative to the plane of the surface unit. The terminal blade includes a tapped thread to permit lead-wire, screw-type connection without the requirement of securing nuts.

5 Claims, 6 Drawing Figures ELECTRIC SURFACE TYPE HEATING ELEMENT AND INSULATOR COMBINATION The present invention relates to a surface-type electrical heating element in combination with an enclosure (hereinafter referred to as an insulator) formed of nonconducting, heat resistant material. In one mode of electrical connection the insulator is used to connect the surface unit to a source of electrical energy. In particular, the insulator permits lead-wire, screw-type connection of the surface unit through a pair of blades carried by the terminal ends to the source of electrical energy while the terminal blades are in the normal disposition for plug-in type connection.

The prior art, as best represented by US. Pat. No. 3,617,703 to William A. Ewart, .lr., discloses a construction somewhat similar to the construction as contemplated herein. Thus, the Ewart patent discloses a combination including a surface-type electrical heating element and a receptacle or terminal block. The surface unit provides a pair of terminal pins ending in a loop. The patent outlines generally what is considered to be the prior art connectiontechniques employed within the industry; namely that in the so-called plug-in type connection the terminals extending from the sheath ends are located in a vertical plane, whereas in the so-called lead-wire, screw-type connection the terminals are located in the horizontal or supporting plane of the surface unit. The Ewart terminal block is used if a lead-wire, screw-type connection of the surface unit terminals to electric power is contemplated. The terminal block provides horizontal openings. Therefore, securement of the terminal loops to electric power requires that the loops be first twisted about their longitudinal axes through an angle of approximately 90. If a plug-in type connection of the surface unit to electric power is contemplated the terminal block is not used The present invention overcomes the abovedescribed problem and as an important aspect thereof provides an insulator adapted to receive a pair of terminal blades of a surface unit for lead-wire, screw-type connection to electric power. Connection may be made without first having to rotate the terminal blades about their axes. To this end the insulator is open at the front to receive the terminalpins in separate chambers. The insulator provides an opening within opposed sides of the body and a slot along opposed sides of the wall separating the chambers. The opening permits access to the connection if the surface unit is to be disconnected from electric power. Connection of each tenninal blade and the electric power leads may be effected without having to first position the insulator in surrounding relation to the connection. A machine screw may be employed for this purpose. A pair of safety tabs on each side of the wall in the region of the slot serve to lock the terminal blades within the insulator once the insulator is moved to the position surrounding the connection or vice versa. The slot serves to accommodate the shank of the machine screw.

As an additional aspect of the present invention the terminal blade is formed by a member which is doubled back upon itself. The blades include a hole or aperture in each portion. A thread is stamped in at least one of the holes. The blade is somewhat resilient in the doubled back condition thereby having the tendency to open thereby to enhance electrical contact when the plug-in type connection of the surface unit is required. The stamped thread obviates the requirement of a nut for receipt of the shank of a screw when coupling the terminal blade to the connector on a lead-wire in the screw-type mode of connection. Preferably, the thread is stamped such that when the member is doubled back it will be directed toward the other aperture. Thus, a smooth surface will be provided to assure maximum area of contact of the terminal blade in wiping contact with a receptacle terminal in the plug-in mode or with a washer-like connection on a lead-wire in the screwtype connection to electric power.

There has thus been outlined in broad fashion an important feature of the present invention for the purpose of better understanding of the same through the more detailed description thereof that follows. Through reading of the more detailed description other features of the invention, forming the subject of the claims appended hereto, will become evident to those skilled in the art. Those skilled in the art will appreciate that the conception upon which this disclosure is based may be utilized readily as a basis for the design of other structures for carrying out the several purposes of the invention. It is important, therefore, that each claim be regarded as including such equivalent constructions as do not depart from the spirit and scope of the invention.

The accompanying drawings illustrate a preferred embodiment of the invention and form a part of the application. By these drawings:

FIG. 1 illustrates in perspective the extending terminals of a surface unit as well as the insulator and terminal blade of the present invention;

FIG. 2 is a plan view, partially in section, of the components of FIG. 1 in the operative condition;

FIG. 3 is a front elevational view of the insulator and terminal blade in the operative condition;

FIG. 4 is a perspective view of the insulator with a portion of the wall broken away to illustrate the internal slot and safety tabs;

FIG. 5 is somewhat similar to FIG. 4 yet further shows in phantom the terminal blade and lead-wire contact assembly; and FIG. 6 is a perspective view of the terminal blade of the invention.

The surface unit, a portion of which is illustrated in FIG. 1, includes a tubular metal sheath 12 of elongated construction. The sheath is generally shaped to a convoluted pattern for supporting a kettle, etc., the contents of which are to be heated. Once the sheath is formed to the convoluted pattern the sheath ends 14 and 16 will be disposed underneath and will normally extend beyond the outermost convoluted race. An electric resistance wire 18 is disposed generally along the axis of the sheath and insulatingly held in that position by refractory material 20. As is well known the refractory material is compacted completely around the resistance wire to maintain its axial disposition. Any process, such as swaging, may be utilized for this purpose.

Cold pins 22 and 24 are Connected to the resistance wire internally of the sheath end and as seen in the Figures extend from the sheath for a short distance. A plug or bushing 26 is received by the sheath at each end for purposes as are known in the art. Preferably, the plug or bushing will be of a compressible dielectric material.

A terminal blade 30 is spot-welded or otherwise secured to the projecting end portion of the cold pins 22 and 24. For this purpose a weld projection 31 may be provided within a channel 32 of the terminal blade. A shoulder or abutment 33 defines the channel end and serves as a stop for the individual cold pin thereby to assure proper orientation of the components prior to the spot-weld operation.

As illustrated to best advantage in FIG. 6 the terminal blade includes a portion 34 and a portion 35 connected to one another by a neck 36. The portions are folded about the neck to reside substantially one over the other. The terminal blade may be stamped from any resilient and conductive sheet metal stock material. The blade may be nickel plated.

The terminal blade construction adapts the surface unit for plug-in connection to a receptacle carried by the range. The terminal blade and insulator also adapt the surface unit for lead-wire, screw-type connection. To. this end both portions of the terminal blade are apertured at 38 and 40. When the portions are folded, as above, the apertures will reside on a common center line. At least the aperture 40 is provided with a stamped thread having the shear marks directed inwardly, i.e., toward the portion 34 of the terminal blade to provide a smooth surface for the purposes discussed above. As will be later discussed a machine screw may be received by the blade thread for the lead-wire, screw-type connection, a mode of connection which may be accomplished because of the new insulator of the present invention. The present invention permits installation of a surface unit by either of the two prior art methods of installation without the requirement heretofore of positioning the terminal blades in one of two planes, i.e., the plane parallel to the plane of the surface unit for the lead-wire, screw-type connection or the plane vertical thereto for the plug-in type connection. The terminal blades need not be rotated through any angle for installation. Since it is unnecessary to twist the terminal blades the possibility of breaking the element electric connection through this operation is obviated.

The insulator 50 may be seen to best advantage in FIG. 4 of the drawing figures. The insulator is formed of an insulating and nonconductive material, such as plexiglass, ceramic or of one of the many phenolic plastic resins. The latter material is preferred.

The insulator includes a body providing a pair of chambers 52 and 54 extending between the front and rear surfaces. A central wall or partition 56 isolates one chamber from the other throughout the body. The insulator is employed in the lead-wire, screw-type connection. To this end the lead-wires 70 connected at an end to electric power, are passed through the respective chambers of the insulator. A washer-like terminal 72 normally will be carried by the other end of each leadwire. A machine screw 74 is passed through the terminal 72 and threadedly received by the terminal blade. The stamped thread in the terminal blade is capable of withstanding sufficient tightening force to ensure a good electrical connection. The stamped thread also obviates the requirement as in prior art installation dates the tip of the shank of machine screw 74.

A pair of safety tabs 62 and 64 project outwardly from the partition near the front of the receptacle. Each safety tab is generally of right triangular form having the base portion toward the slot end. As seen clearly in FIG. 2 the safety tabs interact with the portion 34 of the tenninal blade to prevent the blade from disengaging in one direction once having been received by the insulator. The terminal blade is somewhat resilient. Following a camming movement of the blade'portion 34 toward the portion 35 which is induced bythe inclined wall of the tabs the portion 34 will slip into the FIG. 2 disposition. An audible sound assures that the lock has engaged. The base of the tabs and the slots 58 and 60 provide proper orientation of the terminal blade within the insulator. As may be apparent the slots may be replaced by a hole in the opposed wall sides of the partition 56. In either case movement of the termigagement of the shank of the machine screw. Cutouts 66 and 68 are provided in the receptacle side walls. The

cutouts permit access to the connection area for-replacement purposes. An aperture having a diameter to permit access to the connection of a screwdriver and withdrawal of the machine screw for replacement of the surface unit may be formed in each side wall. The aperture may be provided in place of the cutouts 66 and 68, as choice dictates.

The electrical connection should follow the grounding of the surface unit, if required. To this end a ground wire having a bracket 82 at one end may be attached to the end l4or 16 of the convoluted sheath.

A plate 83 received on the sheath ends provides a ground in the plug-in mode of operation. The plate additionally serves to maintain stability of the sheath ends at the point of connection. As seen the sheath ends are passed through spaced apertures in the plate and suitably welded, staked or otherwise connected to the plate. A tension clip may be carried by the plate. If the surface unit is to be connected to electric power through the plug-in technique the tension clip is removed by a slight rotational movement to break it away from the plate itseltYThe tension clip may be retained if the surface unit is to be connected to electric power through the lead-wire, screw-type technique. In this adaptation the tension clip serves to prevent rotation of the surface unit in the range top.

As noted in FIG. 1, a notch 84 may be provided in one side wall and similarly in the center partition (not shown) of the insulator. The notches willbe of such dimension to accommodate a single or both electrical lead-wires 70 thereby to provide strain relief.

As can be seen from the above, the present invention permits a single surface unit to be connected to electric power by either of the known prior art techniques. Connection using either technique may be carried out with the terminal blade in the same orientation. Thus, the requirement in the prior art to twist the terminal blades with the ensuing possible problem as heretofore noted is overcome. Further, the terminal blade of the present invention is provided with a stamped thread permitting electrical connection without the requirement of an additional securing nut. The benefit of this feature, cost-wise should be apparent. Additionally, the insulator of the present invention permits connection to be carried out before the insulator is moved to connection surrounding relation. This feature provides a clear benefit in ease of installation. Other benefits of the present invention will be clear to those having skill in the arts to which this invention relates.

Having described the invention, I claim:

1. In combination: a surface-type electric heating element comprising a sheath member, said sheath member being in the form of a relatively flat convoluted winding, heating means formed by a resistance wire, means for supporting said wire within and in electrical insulated disposition in relation to said sheath, a pair of pin elements connected to opposite ends of said resistance wire, said pin elements being disposed below the plane of said winding and extending outwardly of the ends of said sheath member, and a terminal blade connected to each of said pin elements and adapted to be connected to electric power, each said terminal blade having a flat face which is disposed in a plane substantially perpendicular to said winding; metal plate means secured to the sheet ends and a connector block comprising a body of electrical insulating material, said body having a pair of compartments for receipt of said terminals, a central wall supported by the top and bottom body wall portion, said central wall defining an insulating medium between compartments, tab means on opposed sides of said wall, said tab means intercooperating with said terminals when received in said compartments to prevent inadvertent release of the same from the block, and said body side walls having access openings to said compartments to permit release of said terminals from said block.

2. The combination of claim 1 wherein each said terminal blade includes a substantially V-shaped portion, one arm of said portion intercooperating with said tab.

3. The combination of claim 1 wherein each said terminal blade includes a tapped thread, said thread adapted to receive a terminal screw to connect said terminal blade to electric power.

4. The combination of claim 3 wherein said central wall includes opposed recesses, each said recess accommodating the shank portion of said terminal screw when said terminal blade is received by said terminal block.

5. The combination of claim 4 wherein each said re cess includes a slot, said slots extending in opposite directions from said access opening. 

1. In combination: a surface-type electric heating element comprising a sheath member, said sheath member being in the form of a relatively flat convoluted winding, heating means formed by a resistance wire, means for supporting said wire within and in electrical insulated disposition in relation to said sheath, a pair of pin elements connected to opposite ends of said resistance wire, said pin elements being disposed below the plane of said winding and extending outwardly of the ends of said sheath member, and a terminal blade connected to each of said pin elements and adapted to be connected to electric power, each said terminal blade having a flat face which is disposed in a plane substantially perpendicular to said winding; metal plate means secured to the sheet ends and a connector block comprising a body of electrical insulating material, said body having a pair of compartments for receipt of said terminals, a central wall supported by the top and bottom body wall portion, said central wall defining an insulating medium between compartments, tab means on opposed sides of said wall, said tab means intercooperating with said terminals when received in said compartments to prevent inadvertent release of the same from the block, and said body side walls having access openings to said compartments to permit release of said terminals from said block.
 2. The combination of claim 1 wherein each said terminal blade includes a substantially V-shaped portion, one arm of said portion intercooperating with said tab.
 3. The combination of claim 1 wherein each said terminal blade includes a tapped thread, said thread adapted to receive a terminal screw to connect said terminal blade to electric power.
 4. The combination of claim 3 wherein said central wall includes opposed recesses, each said recess accommodating the shank portion of said terminal screw when said terminal blade is received by said terminal block.
 5. The combination of claim 4 wherein each said recess includes a slot, said slots extending in opposite directions from said access opening. 